Friday, August 20, 2010

Calls were coming in to the BirdWatch Ireland headquarters about several new bird species with orange crowns. These new birds were hanging around with the old Irish bird regulars like the House Sparrows and Starlings but not in any field guides.

“Rather than being some exotic new visitor, these in fact ARE Starlings and House Sparrows that have been feeding on a plant called New Zealand Flax (Phormium tenax). Though native to New Zealand, this species has been planted commonly in gardens around the country and has even become naturalized in the wild in many areas. Its high antler-like flower-stalks which grow out from the centre of a fan of long, narrow leaves are highly distinctive and will be familiar to many people.

We are used to plants being pollinated by insects and even by the wind, but New Zealand Flax uses another method: it is pollinated by birds. The tubular flowers produce rich, sweet nectar that many birds find irresistible. As they stick their beaks down into the flowers to feed, a small brush-like appendage dusts the tops of the birds’ heads with brightly colored pollen, staining it a vivid orange or red color. When they move on to feed from another flax flower, these birds bring the pollen with them, helping the plant to reproduce.

Image via WikipediaIn New Zealand the main pollinator is a unique native bird called the Tui (Prosthemadera novaeseelandiae), which has even evolved a beak with exactly the same curvature as the flax flower to allow it to feed more easily. We don’t have any Tuis in Ireland, so the plants have to make do with the Irish birds, mainly Starlings and House Sparrows, that have learned that flax nectar is a good source of food.

The staining on the bird’s crown feathers is only temporary and doesn’t cause them any discomfort or harm: they are probably completely unaware of how odd they look to our eyes. It is not at all surprising that people think they have seen a new species of bird, as the addition of such a vivid splash of colors to otherwise rather drab and muted species really catches the eye and stands out as something unusual. It will be interesting to see whether this feeding behavior spreads to other bird species and whether it aids the spread of this invasive plant species in Ireland.”